Diode to ground between coils in series?

[gil]

Hullo! This is my first post, despite lurking for a while.

Recent research into diode clipping has led to a (potentially foolish) train of thought. Assuming we have two pickups that are originally of equivalent phase and polarity which are then combined out of phase, we can generally assume the result to sound 'hollow' due to phase cancellation. Theoretically, if a single diode were used to asymmetrically clip the output of one of the pickups, there would be less phase cancellation on one half of the wave, which I'm guessing would result in a somewhat more 'square' output with a high amount of 2nd-harmonic content.

I'm not certain it'd sound pleasant, but I'd like to try it - which leads me to my question, how could this be implemented in a real circuit? The only concept that comes to mind after a brief amount of thought is inserting a diode to ground between two pickups in series, and I'm having trouble visualising exactly how this would work out.

To give an example, the negative of a neck pickup is connected to ground, while its positive is connected both to the bridge pickup's 'positive' and a diode (which goes to ground); the bridge pickup's 'negative' is connected to our volume/tone circuit. It seems clear that the neck pickup will be asymmetrically clipped, but how does the diode affect the bridge pickup? Would the result differ in an interesting way if the pickups were in phase? Most importantly, am I at risk of electrocution if I try this myself?

Thanks for your patience!

[sumgai]

gil,


Welcome to The NutzHouse!


You raise an interesting point. By tapping the signal at the junction point between the two pickups in series, you are changing the point of how soon and how much the signal will be affected, when compared to the usual method of placing the diode between any pickup combination and the controls/output.

Since a diode can only conduct one half of the signal (positive or negative) after it has turned on, both pickups will be affected equally, even though you are thinking in terms of "across only one pickup". No, the remaining pup is still in the circuit, and it's generating a voltage also, so it must be considered at all times, as well. Further, diodes are not frequency-sensitive, so it won't matter if the pups are in phase or otherwise, the electrical results will be the same. However, being OoP will still affect your overall tonal output, as expected.

Moving the diode may or may not sound good to you, only your ears can be the judge of that. However, JohnH, ashcatlt and other members here have done a pretty hefty amount of work on this topic, so let me suggest that you use our Search function (in the menu above), and look for "diode clipping", for starters.

HTH





sumgai

[JohnH]

Hi gil and welcome.

An interesting idea. I tried a few versions of using diodes to passively clip guitar signals, but based on clipping the whole signal. Generally they were disappointing, but what you are suggesting is a bit different. Probably quite a subtle effect, but worth trying I think. I'm assuming you would take two coils or pickups in series and put a diode across one of them, maybe from the join between he coils and ground. It would be worth trying both in and out of phase.

The type of diode that will work best needs to be able to clip at a very low forward voltage. Normal silicon diodes are no good for this, but either a Schottky or a Germanium type would be likely to be best.

There is no risk to safety by doing this. The only risk is wasting a $ or two on diodes, plus some time.

[JohnH]

Further on this, it occurs to me that the ideal test bed for your idea is a Les Paul or similar, with a rear-accessed control cavity such that one can get in and quickly try stuff with alligator clips. I have such, and it also has series/ parallel and phase switching between pickups, plus I have a few of the right diodes. If you wish, I could test the concept -its interesting enough to want to know! Or, Ill leave it to you to try.

Either way, thanks for posting an original idea.

[gil]

Thanks to both of you for your speedy replies - an earlier search for 'diode clipping' yielded the excellent 'Black Ice'/passive distortion thread of JohnH's, but nothing in the way of this particular arrangement. I'll look again to be sure.

Sumgai, it's good to know I'm on the right track w/r/t both pickups being affected, and knowing that it'll function both in and out of phase is very helpful!

JohnH, thank you for your advice! Normally I'd try this out with my Tele for ease of alligator clipping, but there's no phase switch in it so it would only be half the picture. I'll try it out with a guitar I'm working on and report back in; I only have 2 kinds of Schottky diodes lying around but that should be enough to tell you whether it's worth investigating! (Especially now that I know it's safe to try out)

Thanks again to both of you - I'll give it a shot and see you on the other side!